1. Field of the Invention
The present invention relates to creepers used by mechanics, and, more particularly, to a creeper having a base and an inclinable back portion.
2. Description of the Prior Art
Creepers having back portions which are inclinable relative to a base portion are well known in the art. Such creepers often incorporate mechanisms which use springs as a source of stored energy to drive the inclination of the back portion, as in U.S. Pat. No. 2,051,563 to Mance and U.S. Pat. No. 2,703,717 to Miller. While these spring type mechanisms offer the desirability of an automatic lifting of the back portion, safety concerns require greater reliability and integrity of locking mechanisms which maintain a selected position of inclination of the back relative to the base. Given that the work environment of a user of a creeper may place the user near high temperature components or machinery in motion, an inadvertent release of the back portion could lead to injury of a user of such a creeper if the spring force causes further inclination of the back portion towards the work object.
Prior art creepers have also incorporated mechanisms for inclining a back portion which include lever arms extending from an edge of the creeper for application of force by the user to incline the back portion. This is found in U.S. Pat. No. 2,054,598 to Goldenberg and U.S. Pat. No. 2,564,323 to Brown. These types of mechanisms avoid the safety concerns involved with the spring type mechanisms discussed previously, in that a release of the locking mechanism will result in travel of the user towards a prone position, and away from the work object, due to gravity forces. However, without the stored energy of the spring, all of the energy required for the inclination of the back portion must come from the force applied to the lever arms by the user of the creeper. As the inclination of the back increases, the force which must be applied to the back portion to gain additional inclination decreases. Therefore, the force necessary for inclination will be at a maximum when the user is in a nearly prone position and would approach zero if inclination were to be continued to a nearly vertical position, since the gravity forces which the user would apply to the back portion would approach zero. Therefore, the mechanical advantage of the lever used to incline the back portion should be maximized during the inclination nearest to the prone position when the required force is at a maximum. None of the prior art which utilizes a lever system incorporates a system in which the mechanical advantage is at a maximum during the initial inclination nearest to the prone position.
Accordingly, it is an object of the present invention to provide a creeper having an inclinable back portion in which the mechanism which provides the inclination utilizes a levered mechanism for which the mechanical advantage for the lever is at a maximum during the portion of the inclination nearest to the prone position when the gravity forces on the back portion will be at a maximum.